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Enhancing light absorption by colloidal metal chalcogenide quantum dots <i>via</i> chalcogenol(ate) surface ligands
摘要： Chemical species at the surface (ligands) of colloidal inorganic semiconductor nanocrystals (QDs) markedly impact the optoelectronic properties of the resulting systems. Here, post-synthesis surface chemistry modification of colloidal metal chalcogenide QDs is demonstrated to induce both broadband absorption enhancement and band gap reduction. A comprehensive library of chalcogenol(ate) ligands is exploited to infer the role of surface chemistry on the QD optical absorption: the ligand chalcogenol(ate) binding group mainly determines the narrowing of the optical band gap, which is attributed to the np occupied orbital contribution to the valence band edge, and mediates the absorption enhancement, which is related to the π-conjugation of the ligand pendant moiety, with further contribution from electron donor substituents. These findings point to a description of colloidal QDs that may conceive ligands as part of the overall QD electronic structure, beyond models derived from analogies with core/shell heterostructures, which consider ligands as mere perturbation to the core properties. The enhanced light absorption achieved via surface chemistry modification may be exploited for QD-based applications in which an efficient light-harvesting initiates charge carrier separation or redox processes.
关键词： colloidal metal chalcogenide quantum dots,light absorption,optoelectronic properties,surface ligands,band gap reduction
更新于2025-10-22 19:40:53
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A Chemically Orthogonal Hole Transport Layer for Efficient Colloidal Quantum Dot Solar Cells
摘要： Colloidal quantum dots (CQDs) are of interest in light of their solution-processing and bandgap tuning. Advances in the performance of CQD optoelectronic devices require fine control over the properties of each layer in the device materials stack. This is particularly challenging in the present best CQD solar cells, since these employ a p-type hole-transport layer (HTL) implemented using 1,2-ethanedithiol (EDT) ligand exchange on top of the CQD active layer. It is established that the high reactivity of EDT causes a severe chemical modification to the active layer that deteriorates charge extraction. By combining elemental mapping with the spatial charge collection efficiency in CQD solar cells, the key materials interface dominating the subpar performance of prior CQD PV devices is demonstrated. This motivates to develop a chemically orthogonal HTL that consists of malonic-acid-crosslinked CQDs. The new crosslinking strategy preserves the surface chemistry of the active layer beneath, and at the same time provides the needed efficient charge extraction. The new HTL enables a 1.4× increase in charge carrier diffusion length in the active layer; and as a result leads to an improvement in power conversion efficiency to 13.0% compared to EDT standard cells (12.2%).
关键词： hole transport layers,colloidal quantum dots,solar cells,chemical orthogonality,surface ligands
更新于2025-09-23 15:19:57
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Freeze‐Facilitated Ligand Binding to Plasmonic Gold Nanorods
摘要： Gold nanorods (AuNRs) are an important class of advanced plasmonic materials, but unlike gold nanospheres (AuNSs) their surface modification is difficult due to the specific surfactant layer of cetyltrimethylammonium bromide (CTAB) resulted from the synthesis. In this paper, a freeze-induced surface modification strategy is proposed for AuNRs. Freezing AuNRs right after a simple wash step can facilitate binding of surface ligands and allow assembly of functional biointerface in a fast time scale. This strategy is simple, fast, versatile, and robust, allowing attachments of different ligand molecules, including organic dyes, poly(ethylene glycol)s (PEGs), and DNAs onto AuNRs without additional reagent. An optimal condition for DNA loading is determined with a matrix driven approach. It is shown that the attached ligand molecules are functional, allowing formation of core–satellite type structures using DNAs linking to AuNSs, or high-density vertical superlattice arrays using PEGylated AuNRs.
关键词： DNA,surface modification,gold nanorods,surface ligands
更新于2025-09-19 17:13:59
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Surface Ligands for Methylammonium Lead Iodide Films: Surface Coverage, Energetics, and Photovoltaic Performance
摘要： Surface ligand treatment provides a promising approach to passivate defect states, improve material and device stability, manipulate interfacial energetics, and increase the performance of perovskite solar cells (PSCs). To facilitate targeted selection and design of surface ligands for PSCs, it is necessary to establish relationships between ligand structure and perovskite surface properties. Herein, surface ligands with different binding groups are investigated to determine their extent of surface coverage, whether they form a surface monolayer or penetrate the perovskite, how they influence material energetics and photoluminescence, and how this combination of factors affects PSC performance. Ultraviolet and inverse photoelectron spectroscopy measurements show that surface ligands can significantly shift the ionization energy and electron affinity. These changes in surface energetics substantially impact PSC performance, with the performance decreasing for ligands that create less favorable energy landscapes for electron transfer from MAPbI3 to the electron transport layer, C60.
关键词： defect passivation,perovskite solar cells,interfacial energetics,surface ligands,photovoltaic performance
更新于2025-09-19 17:13:59
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Effect of surface ligands with different terminal group on the optical stability and cytotoxicity of CuInS <sub/>2</sub> /ZnS quantum dots with the crystal structure of sphalerite
摘要： A novel method for preparing CuInS2/ZnS quantum dots (CuInS2/ZnS QDs) with the crystal structure of sphalerite by one-pot hot injection was developed in this paper. The as-prepared core CuInS2 quantum dots (CuInS2 QDs) was uniform spherical nanoparticle with the average diameter of about 2 nm with the ?uorescent quantum yields (QY) of about 2.6%. By capping a shell of ZnS on the surface of CuInS2 QDs, the formed CuInS2/ZnS QDs exhibited obvious enhanced ?uorescent emission with the QY of about 20%. Intriguingly, the crystal structure of obtained CuInS2/ZnS QDs is sphalerite, which was con?rmed by XRD. Considering the different terminal group between these small organic molecules, mercaptoacetic acid (TGA), thioglycerol (TGC) and mercaptoethylamine (MEA) were further selected as capping molecules to exchange the surface ligands of CuInS2/ZnS QDs. The obtained CuInS2/ZnS QDs modi?ed with TGC exhibited excellent photostability in physiological conditions. To investigate the effect of ligand molecules on the biocompatible of CuInS2/ZnS QDs, the experiment on the cytotoxicity of CuInS2/ZnS QDs to A549 cells were conducted. The results indicated that CuInS2/ZnS QDs capped with TGC showed the lowest cytotoxicity while CuInS2/ZnS QDs capped with MEA exhibited the highest cytotoxicity among the three types of CuInS2/ZnS QDs modi?ed with ligands with different terminal group. These results provided a sight on how to select surface ligands to modify CuInS2/ZnS QDs when CuInS2/ZnS QDs will apply in biological ?elds.
关键词： sphalerite,photostability,CuInS2/ZnS QDs,cytotoxicity,surface ligands
更新于2025-09-16 10:30:52